Fabrication And Properties Of Yb³⁺ Doped CaF₂ Transparent Ceramic

Fluoride compounds are very attractive materials for the optical applications. Compared to oxide-based matrices, they present additional advantages such as a high transparency in a wide wavelength region from the VUV to the IR and a low phonon energy that decreases the nonradiative transition probability of the active ions. The trivalent ytterbium, Yb3+, is very attractive as a luminescent ion for laser application because it has a simple two multiplet electronic structure which avoids losses by cross relaxation or up-conversion. In addition, its low quantum defect enables high lasing efficiencies, its broad absorption band facilitates diode pumping and its broad mission band is suitable for ultrashort laser pulse generation or laser wavelength tunability. A lot of works have been done about CaF2 single crystal, but the CaF2 crystal has several disadvantages, such as its fabrication process is very complicated and it is hard to fabricate in a large size and with Yb3+ high concentrations, and all these disadvantages have limited its application. But CaF2 transparent ceramics could substitute for single crystal if synthesis methods of CaF2 powders and ceramics are adopted.In the present work, by direct precipitation method were used to synthesis the Yb3+:CaF2 nanopowders, The relations between the synthesis technology and the performance of the powders have been investigated systematically, while the effects of sintering conditions on the optical properties of the ceramics have also been discussed.Firstly,by direct precipitation method were used to synthesis the Yb3+:CaF2 nanopowders, X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM), absorption spectra test were used to investigate CaF2 particles, and the effect of different reaction medium and the effect of different reaction conditions on the grain size, distribution and morphology of CaF2 was researched. The results show that CaF2 nanoparticles with an average diameter of 50 nm were synthesized in second deionized water and the value is 20nm in ethanol solution, respectively.Secondly, the well dispersed nano powder was used to prepare high density Yb3+:CaF2 ceramic by hot pressed method. powder properties, the effect of sintering temperature, holding time on the optical properties of the ceramics have been discussed. We fabricated different concentration Yb3+ in calcium fluoride at the best sintering conditions. It is found that the samples cracking can be ease by prolonging the holding time or increasing the sintering temperature...